I try to have an objective look on the history without the religious element to it. This second look always helps with better understand of events, in any case history needs to be studied in 3 dimensions. By collecting bits and pieces, you can trace history down to its actual cause. The roots of this conflict are infested in Hashmite vs Ummyad nationalism, nothing to do with religion. The two were major power factions in pre-islamic Arabia vying for the throne of Makkah and situation essentially remained unchanged afterwards. Precisely the reason why Ummayads were swift to shift the capital away from Medina to Damascus to make it as far away as possible from Hashmite power center in Mekkah!